November 11, 2012

(Phys.org)—A team of scientists from the Naval Research Laboratory, Old Dominion University, and the University of Waterloo reports the first direct evidence that emissions of carbon dioxide (CO2) caused by human activity are propagating upward to the highest regions of the atmosphere. The observed CO2 increase is expected to gradually result in a cooler, more contracted upper atmosphere and a consequent reduction in the atmospheric drag experienced by satellites. The team published its findings in Nature Geoscience on November 11, 2012.

The team of Dr. John Emmert, Dr. Michael Stevens, and Dr. Douglas Drob from NRL's Space Science Division; Dr. Peter Bernath from Old Dominion University; and Dr. Chris Boone from the University of Waterloo in Canada studied eight years of CO2 measurements made by the Atmospheric Chemistry Experiment (ACE), a scientific satellite mission funded primarily by the Canadian Space Agency. ACE determines vertical profiles of CO2 and many other atmospheric gases by measuring how the atmosphere absorbs sunlight at different wavelengths as the Sun rises and sets relative to the spacecraft.

CO2 concentration at 100 km altitude (~62 mi) measured by ACE (blue circles) and predicted by a model of the chemistry and physics of the global upper atmosphere (green crosses). The purple line shows the linear trend of the ACE data. Credit: U.S. Naval Research Laboratory

CO2 occurs naturally throughout Earth's atmosphere and is the primary radiative cooling agent in the energy balance of the mesosphere (~50-90 km altitude) and thermosphere (>90 km). The same properties of CO2 that cause it to trap heat in the troposphere (<15 km) make it an efficient cooler at higher altitudes. The difference is that at high altitudes, the density of CO2 is too thin to recapture the infrared radiation (heat) that it emits. "In the upper atmosphere," explains Emmert, "thermal energy is transferred via collisions from other atmospheric constituents to CO2, which then emits the energy as heat that escapes to outer space."

The enhanced cooling produced by the increasing CO2 should result in a more contracted thermosphere, where many satellites, including the International Space Station, operate. The contraction of the thermosphere will reduce atmospheric drag on satellites and may have adverse consequences for the already unstable orbital debris environment, because it will slow the rate at which debris burn up in the atmosphere.

It has been expected that anthropogenic CO2 increases are propagating upward throughout the entire atmosphere. Before the study of ACE data, CO2 trends had been measured only up to 35 km altitude, although indirect evidence from satellite drag studies indicates that the thermosphere is indeed slowly contracting. The scientists estimate that the concentration of carbon near 100 km altitude is increasing at a rate of 23.5 ± 6.3 parts per million (ppm) per decade, which is about 10 ppm/decade faster than predicted by upper atmospheric model simulations. In comparison, tropospheric CO2 concentrations are increasing at a rate of about 20 ppm/decade (the current concentration of CO2 near the ground is ~390 ppm). The authors speculate that the larger than expected upper atmospheric trend may be caused by changes in upper atmospheric circulation and mixing.

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10 comments

This study alone shows how ridiculous global warming hysteria is. Why was this study conducted? Simple. Someone applied for grant money by saying in the application that they were going to study the effects of rising CO2 on space junk. And here is this silly study. And meanwhile tax dollars are wasted on this drivel.

The devil is smiling as dollars that could be used to help the needy are wasted on this nonsense instead.

lino235 studies of this sort come out every day, something ever so tenuously linkeable to 'global warming'.

sattelites? gravity? atmosphere? c02! basically as long as you have your 6 degrees of separation you can find money to write and article about something related to global warming. as with any organized human endeavor , doing science costs money, and thus is limited in its scope by the people handing out the money. the problem is that the biases of those people are frequently aligned with concerns other than promoting the best use of funds for studying interesting scientific questions.

science can study if cucumbers float better in warmer water than colder water, but is it worthwhile science? the answer is obviously no. USEFULL science is very important. of course while we cannot always know what science will turn out useful, we can get a grip on what scientific projects will most likely be useless.

psuedo science is one issue and then there is just bad wasteful research

It has been known for decades that greenhouse warming in the lower atmosphere will most likely trigger cooling and contraction in the far upper atmosphere. The air force has been modeling this since the 1970s. But this article is very poorly written. If you are confused by this article you should be. For instance, instead of quoting from the paper they quote from third parties that are NOT atmospheric scientist. See the comment by Hugh Lewis.Either he is misquoted or he doesnt know anything about how the earths troposphere works.

"Here, we present direct evidence that CO2 concentrations in the upper atmosphere are increasing." - Paper in question

More..

" We analyse eight years of CO2 and carbon monoxide mixing ratios derived from satellite-based solar occultation spectra. After correcting for seasonal–latitudinal and solar influences, we obtain an estimated global increase in COx (CO2 and CO, combined) concentrations of 23.5±6.3 ppm per decade at an altitude of 101 km, about 10 ppm per decade faster than predicted by an upper atmospheric model."

Summary, high altitude effects are being observed in accordance with expectations, but vertical mixing is higher than anticipated explaining some secondary effects of global warming that have been observed but who's rates have not been explained.

Once again the Denialists are found to be incapable of comprehending the information provided to them.

It is a Conservative brain wasting disease. Terminal in all known cases.

Ok so this means that even though the lower atmosphere will warm significantly it won't expand correspondingly at all? I stubbed my toe time commission a study to find how global warming is at fault for that too.

Both the temperature and density of the atmosphere change with altitude, as does it's emission spectra.

The measurements and observations stated in the Nature Geophysics article document changes in the upper atmosphere which were projected by climate models and now confirmed in kind.

Observation trumps Denialist Dogma ever time.

This is a pleasant aspect of reality.

Davdaddy- While your getting that toe looked at, see if they will let you read any articles regarding the collapse of the thermoshpere. If you even remotely understand the concepts behind thermal contraction or expansion and the IR absorption/emission properties of CO2, it is literally a no brainer. It actually becomes unsettling when you factor in water vapors ability to do this as well, and how much more of it the atmosphere can and it holding at any given time. What is a positive feedback in the troposphere creates a negative one in the layers above it.

"Ok so this means that even though the lower atmosphere will warm significantly it won't expand correspondingly at all? I stubbed my toe time commission a study to find how global warming is at fault for that too."

But

The lower atmosphere (troposphere), where the greenhouse warming occurs, will indeed expand due to warming. But while containing most of the mass it occupies only a tiny volume of the atmosphere.

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